Texas Instruments LM3420AM5X-12.6

Overview

LM3420AM5X-12.6 from Texas Instruments (formerly National Semiconductor) is a precision shunt-mode lithium-ion battery charge controller IC designed for 3-cell (12.6 V nominal) pack end-of-charge regulation. It integrates a temperature-compensated bandgap reference (±0.5% initial tolerance), open-emitter NPN output transistor (15 mA drive), internal feedback resistor (287 kΩ), and compensation-capable op amp in a SOT-23-5 package. It serves as the voltage-sensing and control element in linear or switching charger topologies.

For engineers reviewing the LM3420AM5X-12.6 datasheet, LM3420AM5X-12.6 pinout, LM3420AM5X-12.6 application, or LM3420AM5X-12.6 equivalent, key selection criteria include its 12.6 V regulation voltage with ±0.5% A-grade accuracy, 85 µA quiescent current, 1.0 V output saturation voltage at 15 mA, internal R_f value of 287 kΩ, and compatibility with external loop compensation via the COMP pin.

Technical Context

The LM3420AM5X-12.6 implements a precision shunt-regulator architecture where the IN pin senses battery voltage and the OUT pin sources current to control an external pass device (e.g., MOSFET or BJT). Its error amplifier features externally accessible inverting input (COMP pin) for frequency compensation, enabling stable closed-loop operation across linear and switching charger designs.

It uses a curvature-corrected bandgap reference delivering <±0.5% regulation voltage tolerance over −40°C to +85°C ambient, with internal feedback resistor trimmed to 287 kΩ (min/max: 215/359 kΩ) to set gain and phase margin. The open-emitter NPN output drives up to 15 mA while maintaining ≤1.3 V saturation at full load, supporting direct interface to optocouplers or base/gate drivers.

Key Specifications

Pinout & Package

The LM3420AM5X-12.6 is housed in a 5-lead SOT-23-5 surface-mount package (NS package code MF05A), with pin 1 marked by a dot. Thermal performance is optimized when pin 5 (GND) is soldered to a PCB copper pour for heat transfer.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar lithium-ion battery charge controller applications.

Compared with LM3420M5X-12.6, the LM3420AM5X-12.6 delivers higher voltage accuracy for safety-critical battery termination; compared with TPS650230RSLR, it offers minimal BOM count and analog-only simplicity for dedicated shunt-control applications.

Availability

LM3420AM5X-12.6 is available at Aetrix Electronics and suitable for portable medical devices, industrial handheld terminals, wireless power tools, and uninterruptible backup modules requiring stable component supply and long-term production continuity.

Supply support for LM3420AM5X-12.6 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments acquired National Semiconductor in 2011 and maintains legacy product lines including precision analog ICs for power management.

The LM3420 series belongs to TI's battery management portfolio, engineered specifically for high-accuracy, low-quiescent shunt-based charge control in single- to four-cell lithium-ion systems.

FAQ

What is the exact regulation voltage tolerance of the LM3420AM5X-12.6?

The LM3420AM5X-12.6 has a regulation voltage of 12.6 V with an initial tolerance of ±0.5% over temperature (−40°C to +85°C ambient), verified per Electrical Characteristics table for LM3420A-12.6 in SNVS116C. This A-grade specification ensures precise 4.2 V/cell termination for 3-cell Li-ion packs without external calibration. The LM3420AM5X-12.6 achieves this via curvature-corrected bandgap reference and factory-trimmed internal components.

How does the LM3420AM5X-12.6 interface with external pass devices?

The LM3420AM5X-12.6 uses its open-emitter NPN output (OUT pin) to source up to 15 mA, enabling direct drive of optocoupler LEDs, PNP transistor bases, or N-channel MOSFET gates (with appropriate level-shifting). The output saturates at ≤1.3 V at 15 mA, allowing sufficient voltage headroom for external device biasing. The LM3420AM5X-12.6 requires an external pull-up or collector load to complete the current path.

Can the LM3420AM5X-12.6 be used in switching regulator-based chargers?

Yes, the LM3420AM5X-12.6 is explicitly designed for both linear and switching charger topologies. Its COMP pin provides access to the error amplifier's inverting input, enabling external compensation for stable loop response with buck, boost, or flyback regulators. Application circuits in SNVS116C (Figures 7–9) demonstrate integration with LM2575-ADJ and other switching controllers for high-efficiency 3-cell charging.

What is the purpose of the NC pin (Pin 5) on the LM3420AM5X-12.6?

Pin 5 of the LM3420AM5X-12.6 is a no-connect (NC) terminal with no internal die connection, but it is a thermal pad designed to be soldered to the PCB ground plane for enhanced heat dissipation. Per NS package documentation (MF05A), this improves thermal resistance (θ_JA ≈306°C/W) and prevents junction temperature exceedance under sustained 15 mA output loading. Leaving Pin 5 unsoldered risks thermal derating and reliability issues.

Does the LM3420AM5X-12.6 support external voltage trimming?

Yes, the LM3420AM5X-12.6 supports ±10% external regulation voltage trimming via resistors connected between the COMP pin and either IN or GND. Trim formulas specific to the 12.6 V version (R_increase = 28×10⁵/%incr; R_decrease = (259×10⁵/%decr) − 287×10³) are provided in SNVS116C Section "VREG External Voltage Trim". This allows fine-tuning for system-level calibration without altering the core LM3420AM5X-12.6 functionality.